The invention relates to a mineral mining installation having a longwall structure, such as a conveyor or a winning installation, and a roof support assembly constituted by a plurality of side-by-side roof support units, at least some of which are provided with hydraulic bracing rams for bracing longwall structure longitudinally.
In installations of this type, it is known to use a so-called block bracing system (block anchorage) for bracing the longwall structure longitudinally. The block bracing system comprises a relatively large number of hydraulic bracing rams, each of which is pivotally mounted between the longwall structure and the floor sill of one of the roof support units. The bracing rams are provided at the two ends of the installation, and are inclined at small acute angles to the longitudinal axis of the longwall structure. The floor sills are provided with brackets for the connection of the bracing rams.
During mining operations, it may be necessary to alter the distance between one or more of the roof support units and the longwall structure, for example to enable the roof bars of the roof support units to be advanced as closely as possible to the face being won. This is particularly important where the face slopes. Any such change in the position of a roof support unit inevitably results in a change in the angle of inclination of the associated bracing ram. This in turn results in a variation of the bracing forces applied to the longwall structure, which is undesirable. In particular, the bracing force decreases as the inclination of the rams increases with an increase in the distance between the longwall structure and the roof support units. This disadvantage can be overcome by adapting the points at which the bracing rams are attached to their floor sills to the changing operating conditions. One way of accomplishing this is to change the connecting brackets. Obviously, the changing of the brackets is time consuming, and requires a relatively large number of standard parts to be kept in stock.
U.S. Pat. No. 4,227,833 describes a mineral mining installation having bracing rams which are connected to the floor sills of the roof support units by brackets which are slidably mounted on the floor sills. The brackets can be moved towards, and away from, the longwall structure, and means are provided for securing the brackets to the floor sills in any one of a plurality of positions. Unfortunately, the use of slidable brackets results in a complicated design, and modifications to the floor sills of the roof support units. Consequently, such an arrangement results in considerably expense. Moreover, slidable attachment of the brackets to the floor sills can impede the movement of personnel along the longwall in an unacceptable manner.
The object of the invention is to provide connection means for such bracing rams which can be produced economically, even in different sizes, and which involves no troublesome expensive design steps as regards attachment to the floor sills of the associated roof support units.
Another object of the invention is to provide connection means that can be attached in a simple and rapid manner to the floor sills of associated roof support units, without materially increasing the height of those floor sills, whereby movement of personnel along the longwall is not impeded in an unacceptable manner.